Pompe's disease or Glycogenosis Type II is a well recognized glycogen storage disease of humans. Glycogen is deposited in tissues due to a deficiency of lysosomal alpha-1,4-glycosidase activity. There is little detailed information on the pathogenesis of the lesions. The School of Veterinary Studies at Murdoch University has acquired a herd of cattle carrying a genetic defect which is expressed in homozygous animals in the form of Generalized Glycogenosis Type II. Affected cattle have shown both the late onset and infantile forms of the disease. We are producing affected animals so that we may study the precise clinical manifestations and the development of the lesions biochemically and by light electronmicroscopy. Serial muscle biopsies are being taken and detailed postmortem examinations are being performed on animals showing overt signs of disease. The biochemical and morphological changes are being correlated. A study will be made on enzyme infusion therapy and we will also attempt to produce chimeras from normal and affected four cell stage embryos.